The Warehouse: The Quest for Crossrail's Missing Cores 00:36, 26 August 2015 John Bull — 53 Comments The squealing of machinery comes to a halt and the large red light on the operator’s panel turns green. A buzzer sounds and he steps forward, opening a salt-encrusted gate to reveal a small miner’s lift. On its floor more salt has formed into small drifts. It has walls on two sides, but apart from a safety bar the back is open, the rear wall of the shaft (and the gaps in it) clearly visible. “If you’re not good with that kind of thing then best face forward.” Says Graeme McDonald, Head of Operations for Deepstore. “Either that or we can just turn our helmet lamps off.” He says with a grin, gesturing up to the empty spot where, in a regular lift, the light fitting would be. The miners’ lift from a distance and then close up. The regular entrance to Deepstore’s facility is closed for maintenance. That this doesn’t stop us from entering is a rather effective demonstration of just what makes this facility so unique.

For this is no run-of-the-mill secure storage facility, nor is it even in London. In fact we are at Winsford Rock Salt Mine in Cheshire, Britain’s oldest active rock salt mine. Deepstore inhabits some of its mined-out tunnels and thus with the main visitor lift out of action we are heading underground the same way the miners do. The fact that we are here at all might seem to be a spectacular case of scope creep on the part of the inhabitants here at LR Towers. Deepstore are underground, certainly, but they are not Underground. Nor, quite obviously, are they within the M25. 150 metres below us, however, lie literally kilometres of London in the form of thousands of broken-down core samples – all carefully collected, compared and catalogued by Crossrail over a fifteen year period. Intended primarily to ensure that no surprises awaited its Tunnel Boring Machines (TBMs) as they carved a path through the ground beneath the Capital, in the process they also expanded our geological understanding of what exactly lies beneath our feet. Down in the mine. Note the remains of an old narrow-gauge railway.

The big question Before looking at the contents of Crossrail’s vault itself it is worth stepping back briefly and looking at the path which led to Cheshire. For the residents of LR Towers this journey began back in 2012 when we looked at the surveys Crossrail had to carry out to ensure the route was free of unexploded WW2 bombs . Whilst there was no need to retain the vast majority of the core samples taken as part of this particular process, it did prompt a question – core surveys to establish the geology of the route had been undertaken since the early nineties… …so where were they? We built this city on rock and loam In the world of geological engineering there is an old adage: “You pay for a quality ground investigation whether you procure one or not.” Karl von Terzaghi, father of soil mechanics The attribution in perhaps apocryphal, but the sentiment is certainly true. Any large scale construction project is at risk of failure if the ground on which it is built is not thoroughly surveyed. This is doubly true for tunnelling, where an unexpected change in the condition of the ground through which you are tunnelling can bring disaster.

This was something Marc Brunel discovered to great cost during his efforts to build the Thames Tunnel , the world’s first tunnel beneath a tidal river. Although his efforts would eventually be successful, unexpected pockets of sand and silt contributed to the tunnel collapses and flooding that would bring the project to the edge of disaster and cost lives. More recently, a similar failure to understand an area’s geology would play a key part in the rampant delays and cost escalations that would plague Boston’s “Big Dig” . Travelling through the mine to the Deepstore facility. It is difficult to grasp the scale. More complex than you think The geology beneath London is frequently over-simplified. The general narrative is often reduced to one where north of the Thames, London is largely clay (which is easy to tunnel) whilst the ground to the south is more problematic. The reality, however, is that over hundreds of millions of years the London Basin has seen vast changes in its makeup. High water levels, flooding, glaciation and a wide variety of other factors have periodically affected the area, and the Thames itself has changed course several times. A conveyor belt stretches out into the distance, carrying salt towards the surface lifts.

All of this has had a profound effect on the geology of the Capital, to the point where a description of what lies beneath Greater London and its surroundings reads like some sort of alternate Shipping Forecast: Lower Greensand, The Upnor Formation, Thanet Sands, Harwich Clay, Shepperton Gravels, Bullhead Beds, Upper Shelley Clays, and more. Though none of that geology is particularly unusual (or indeed unfriendly to tunnelling) it still needed to be charted. And just as similar surveys for the Jubilee Line extension had significantly expanded our geological understanding of the London Basin, so too did Crossrail. Most importantly, from an engineering perspective, it revealed the existence of at least eight more geological faults beneath the city than were previously known – something that, alongside the discovery of a number of geological scars, necessitated extra work at Farringdon station and some subtle changes to tunnel depth and cross passage location beneath the Thames. A salt bridge over lower works, lit only by the headlights of our minibus, on route to Deepstore Keeping the cores Given the geological tale they tell, keeping core data has long been an established part of tunnelling, especially with regards to the Underground.

That information can be useful long after a core was drawn if ground conditions change. This may seem like an infrequent occurrence, but within the last few years London Underground have had reason to look at old ground data again not once but twice – when issues related to London’s rising water table (in part the consequence of changes in the level of heavy industry in the capital) affected both the Jubilee and Northern lines in different ways. In recent history this philosophy has expanded to include the retention, wherever possible, of the original cores as well as the data produced, and such was (and remains) the case for Crossrail. Which brings us back to our earlier question – where are the cores stored? Emerging into the light at the Deepstore facility. The vehicles gives a sudden sense of scale. In the short term, the location of those cores was relatively easy to trace – a large rented warehouse in Canning Town, East London. This would never serve as a permanent home, however, because the cores would need to be kept in a climate-controlled facility to prevent deterioration, a potentially costly exercise for an organisation critically aware of its need to be seen as constantly seeking value for money.

At the time Crossrail were unable to confirm to us precisely where they intended to store them in the long term. Work underway to expand Deepstore’s storage areas. Getting by with a little help from a friend That this question continued to occasionally prey on our minds may seem strange, even for the residents of LR Towers. That it did was largely down to some basic back-of-the-envelope mathematics – Crossrail had dug some 300 boreholes. Generally these ranged from 40m – 60m in depth, but occasionally they reached over 100m. Broken down into sections small enough to be shipped and stored this translated to an awful lot of containers, and thus by definition a particularly impressive place to keep them. As is often the case with such things, in the end the answer ultimately emerged almost by accident. Whilst researching TfL’s move from 55 Broadway, it became clear that they would require additional space in which to store their own archive and other materials. Storage space waiting to be populated at Deepstore. Document storage in Deepstore.

TfL’s archive (and its management) is a worthy topic in its own right and one to which we will return in a future article, but what mattered at the time was that TfL publish all expenditure over £5000 in their public accounts and thus their partner in this exercise was easy enough to determine – Deepstore. Crossrail have always enjoyed a close relationship with TfL, not least because the latter is one of the former’s project sponsors. This even extended in early years to secondment of staff and resources from TfL to Crossrail. It thus seemed logical that when looking for a place to store cores Crossrail’s first call would have been once again to their organisational friend and their supply chain. If TfL used Deepstore, we thought, then perhaps Crossrail did too. Floor to ceiling document storage. A vault like this can store approximately 150,000 boxes in this way. Discretion over secrecy It should be emphasised that Crossrail themselves were happy to confirm this was the case when asked, just as TfL were happy to confirm their own relationship with their out-of-London archive. Indeed both organisations are justly proud of their current setup.

It was discretion, rather than secrecy on their part (as well as Deepstore’s respect for the privacy of their clients) and our own low level of interest in finally solving the mystery that had resulted in it lying unsolved for so long. Nonetheless, solution brought a sense of satisfaction. In Deepstore both TfL and Crossrail had found a perfect storage partner. Deepstore Part of Compass Minerals, Deepstore was set up in 1998 to take advantage of some unique attributes identified in its Winsford Mine. Located only 150m below the surface, the mine almost naturally maintained a temperature of 14°C. As a salt mine, it was also dry. Almost since it opened, salt has been excavated from here in a grid pattern, leaving large, regular, pillars to maintain the integrity of the mine. By 1998 this meant that Winsford was a near-natural climate-controlled environment blessed with wide open passages and easily configurable chambers. In other words, it was as close to a perfect place to store archival documents and other items as one was likely to find, and Deepstore was born.

Engineering entry The same discretion that, until now, has kept both organisation’s presence in Cheshire generally out of the public eye also meant that engineering a visit was also something that required some effort – much of it on the part of the press offices at both organisations rather than ourselves. Finally, however, this week saw ourselves and fellow rail and London obsessive IanVisits make the trip up north. Moving through Deepstore. Outside Crossrail’s vault at Deepstore. This article ultimately represents the result of that exercise, with the photos hopefully providing as good an impression as one might get on screen of what we found. As a facility, Deepstore itself is impressive. The sight which greeted us on entering Crossrail’s vault, however, confirmed our mathematical suspicions: Crossrail had certainly required a very large area for their stored cores. First sight of the Crossrail vault. The scale of the vault is difficult to fully describe – at least not without resorting to comparisons with films such as Indiana Jones, or shows such as Warehouse 13. The vault is full of carefully stored and labelled pallets, each of which contains a selection of cores from a particular section of the Crossrail route. Rows upon rows of core sample boxes can be found in the vault.

Having been lucky enough to secure the company of Crossrail Geotechnical Specialist John Davis for our expedition, we are able to open a number of crates to see the cores therein. Boxes open, wrapped core samples visible. Fascinatingly, in many cases once unwrapped the differences between the geology of differing cores is very obvious. Generally speaking they are also both intact and in good condition, thanks to the climate controlled environment. Some of the more brittle cores have cracked and split, but this is expected and not considered a problem. Something that’s hard to capture on film is the width of the vault as much as the depth. In part this is perhaps because it is an “L” shaped space, stretching well round the corner from the entrance. Crossrail assure us they have top men working on these cores. Top. Men. A certain sense of atmosphere is also added to the scene by the fact that many of the crates have off-white labels that have acquired a layer of dust. It gives an impression of age that isn’t entirely accurate, at least not yet. It’s a curious effect, which seems to add a sense of gravitas to the space.

Visual dramatics aside, however, it does also repeatedly demonstrate how well Crossrail’s cores have been categorised and labelled. Something that will prove an enormous advantage to those engaging in future study. A closer look at the crate labelling, which is highly precise. That said, there’s no escaping the fact that despite the space, it is at least in some places closely packed with pallets. Something that really highlights the overall length of core samples taken. Crates of cores packed tightly together. Finally, tucked away in the corner, is evidence that TfL’s active cooperation with Crossrail is far from over. Clearly lacking a similarly configured space at Deepstore (TfL’s vault space is largely setup for documents), they have borrowed some space in which to store their own cores. These cores, produced for the Northern line extension, help highlight that construction work – and planning for it – never stops on the network. Less neatly packed but equally useful – TfL’s cores. Amongst these samples is a large box marked as being from “Battersea Dog & Cat House” containing a large number of closely packed cores.

A small mystery solved Ultimately the resting place of the cores was merely a minor mystery, one without real effect beyond establishing that the cores themselves were preserved for current and future generations to study. Nonetheless it is somewhat gratifying to have an answer as to their location. And if nothing else that locations serves to highlight once again just how large a project Crossrail is, and how carefully it is being managed to ensure success. Our thanks to Deepstore, Tfl and in particular to Crossrail for successfully navigating the paperwork to enable a trip to vault. 26 August 2015 at 01:45 Interesting stuff. Minor corrections: the Big Dig was in Boston, not Chicago; and in the last sentence, sate-managed I think should be site-managed. RichardB 26 August 2015 at 08:02 The National Archives also use this facility to house the growing volume of records which cannot be housed at Kew.

A lot of research was undertaken to confirm the stability and appropriateness of the environment before proceeding but the scale of the mine means there is colossal spare capacity which is a relief as whilst there are assumptions that the switch to digital media will mean less physical records will need to be added to the archive in the future there is still an awful lot of paper to come not least because the archive is still dealing with records created over 25 years ago. Anonymous 26 August 2015 at 08:44 @JB – for those of us with a squirrel-like interest in outre info (it’s called Positivism in more polite circles) , I thought this was a fascinating article. The saltmines need only the usual m******* and command centre to become Blofeld’s next seat of power.

ngh 26 August 2015 at 10:00 Karl von Terzaghi did his key work on the maths of soil mechanics in the mid 1920s and this filtered through to structures in the UK in the mid 1930s onwards which is worth bearing in mind when there is talk of reuse or rebuilding structures in and around London… He also did a lot of key work on drainage and embankment stability. [Will there be an LR Christmas quiz question on which Tergaghi engineered buildings featured in Indiana Jones films?] John Bull 26 August 2015 at 10:03 A fascinating insight JB, thank you. I did wonder at first whether I was looking at pallets of hot-off-the-press LR Magazine! You joke, but I suspect there’ll be a brief period between them arriving here Thursday and us getting them all out to buyers where there’ll be a similar scene on a smaller scale. I fully intend to tweet a photo of our full print run before we unpack it. Greg Tingey AND a white Cat. That RBGK are using the place as well is fascinating.

Of course salt is corrosive to metals in the presence of water, but it is dry down there, so just brush your shoes very carefully when you leave …. They have their own web site: HERE And here’s an old Grauniad article on the subject. Walthamstow Writer 26 August 2015 at 10:05 If nothing else this sort of article helps explain why big construction projects can cost money. There are all sorts of “odd” but essential activities like these which are required to ensure any future issues can be dealt with and commitments in the enabling legislation met. Having worked alongside a chap who was dealing with claims and issues arising out of the JLE and its construction years after the line was opened then I know that a similar set up exists for Crossrail and no doubt will for the NLE and Croxley Link. Snowy 26 August 2015 at 10:26 A fascinating article thanks, made more so by having read IanVisits twitter feed of the trip (sickness included, was the underground minibus trip bumpy per-chance?). It’s an incredible wealth of information in a geological sense, how do they intend on using it for future?

Will they hire out the cores or allow visits for future project engineers (free or paid for to help support the facility costs) or will this mainly be for academic interest? Graham H 26 August 2015 at 10:40 @ngh – and it’s the lack of knowledge about soil mechanics pre-Terzaghi that causes so many problems with dealing with that 95% of the railway infrastructure built before WW2. In particular, the Victorians simply created embankments by tipping, not even consolidating, the substructure. @WW – I agree entirely with you about the hidden cost of maintaining all this “evidence” – another (and relatively recent) reason for doing so is for the purpose of handling future insurance and legal liability claims alas. timbeau I love the photos, as well as the article itself. It’s a fascinating read. But… “The geology beneath London is frequently over-simplified. The general narrative is often reduced to one where north of the Thames, London is largely clay (which is easy to tunnel) whilst the ground to the south is more problematic. “ In fairness, this was indeed true when most of the Underground network was being built.

It’s only relatively recently that tunnelling technology has reached the point where we can dig them pretty much anywhere we choose. The development of the TBM has played a large part in this and is probably due an article on the technology and its history. (I can remember reading about the “drum diggers” employed on the Victoria Line, which were a direct ancestor of the modern TBM.) Even so, the geology beneath London varies sufficiently that there are different types of TBM being used on Crossrail: Some use the more conventional cutting heads, while others employ a slurry shield to help them chew through softer, water-bearing ground. Vince I see the same mine is about to feature on BBC London lunchtime news. LR beats the BBC! John Bull 26 August 2015 at 13:32 I see the same mine is about to feature on BBC London lunchtime news. LR beats the BBC!

If you see me in the Rose & Crown some time, buy me a pint and I’ll give you my opinion on the story-finding abilities of 90% of broadcast journalists… Pedantic of Purley 26 August 2015 at 14:42 It is true that additional geological information necessitated extra work at Farringdon but it is also true that yet further information revealed that this was not as much as at first feared. Initially the fear was that, apart from anything else, the geological faults would mean that “lenses” – small pockets of waterlogged soil would be present. Further examination and analysis let to them being fairly confident that these would not be there so the tunnelling strategy did not need major modification for this reason. As stated by others, nowadays it is an awful lot more scientific and things are much better known and understood than the they were in the days of City & South London construction. As indicated in the article, we are starting to see the Northern Line Extension go through the same process of more detailed knowledge and already provision for compensation grouting at one site has been deemed no longer necessary as a result of better geological knowledge of the area.

emmeagle [If there is something specific that adds to this article or the comments, by all means draw our attention to it. However LR is not a news posting service so this comment has been snipped. LBM] Fandroid 26 August 2015 at 17:04 It is a sobering thought for us engineers of a later (much more complicated ) age that the Victorian engineers achieved so much with only basic geological knowledge and just about zero soil mechanics analysis. The railway engineers followed close on the heels of the canal engineers, where getting it wrong could be very messy indeed. Then you have to think of some rather large dams, holding back humungous volumes of water (and they still do!). There were some fatal dam failures, but really not very many. The railway builders did not formally compact their embankments, but as the spoil delivery systems consisted of lots of small volumes dumped by people and horses walking over that which had already been dumped, the resulting compaction was probably just about ideal!

ukmoose 26 August 2015 at 17:31 As a geologist I have been to many core stores around the world, I would have expected photographs more like the photo you included of the document storage than of core still sitting on pallets. I’m surprised that Crossrail and Tfl has chosen to store the core data themselves rather than outsource this to either a company that specialises in core storage or to store it within the National Archive at the British Geological Survey. There are several companies who do this in the UK storing hundreds of kilometres of core for the oil industry. What is more surprising is that it would appear that core collected for crossrail in the 1990’s is already being stored with the BGS as is data from the jubilee line extension ( search for Drill Core and Borehole Scans) In all licences for oil and gas exploration there is a clause that states that any core collected must be kept in usable condition in perpetuity. Core and other samples are kept confidential for a period of time, but they are then released (often in as little as 4 years) and are available for studies and research both by academia and other companies.

There is also a central record kept of all oil and gas wells that are drilled in the UK, so it is a simple task to know what data exists and who to contact to gain access to it. The challenge of storing the geological data themselves is will Crossrail/Tfl have the expertise in managing the core 10 or 25 years time? How do others or future rail projects find out it exists and who to contact to gain access to it? Anonymous^2 26 August 2015 at 21:54 Regarding the apparent lack of soil compaction by Victorian constructors … I believe it was standard practice for newly constructed railway lines to offer only a freight service, normally coal trains, for six months or so while everything settled down. While this may have been to compact the ballast before tamping machines were invented, it could also have had some beneficial effects on the sub structure.

Graham H 26 August 2015 at 22:24 @Anonymous 2 -I was surprised by this – the histories of virually all the railways I have read show the service commencing the moment the Inspectorate had certified the works to be complete (usually the next day) – can you cite some actual cases? {Many lines had very little coal traffic and many minor lines justified at best a short pickup freight each day.]. Jonathan Roberts 27 August 2015 at 05:14 @Graham H Try the Settle-Carlisle Line -freight from August 1875, passengers from April 1876. The Great Central’s London extension opened for coal trains in July 1898, passengers from March 1899 and other freight from April 1899. Of course, freight and especially coal was the primary earner for Victorian main line railway companies, so there was a commercial and shareholder reason for getting freight running as soon as possible, quite apart from any benefits of track or ground consolidation.

On secondary and branch lines, it may have been less critical, but those companies would have been desperate to get every little bit of revenue from whatever source, at once! It wasn’t untypical for passenger revenue still to be in a minority on lines such as the Midland & South Western Junction – there, crudely, passengers were a quarter to a third of income, freight a half, and parcels mail etc the rest, along with a little from other ancillary income. Greg Tingey Compaction, opening dates & intervals etc. A line could be opened for freight only, with much fewer restrictions than for passengers. In some cases, I believe freight openings occurred without formal HMRI inspections, but, even so, the standards required, even then, for passenger operations was much stricter than for freight, so it is no surprise that one gets intervals as listed by Mr Roberts, notwithstanding the commercial imperatives of freight operation. Graham H 27 August 2015 at 09:14 @Jonathan Roberts/Greg T – the trouble with your argument is that for every case where there was a six month delay, you could find many where there was none.

For example, to take three random examples off the Hewett bookshelf, the Wycombe – Thame- Oxford line, the Guildford New line, and that archetypal coal line – the Hull and Barnsley (where passenger followed freight within a week). In the examples you cite, JR, it would be necessary (to avoid the post hoc propter hoc argument) to show that consolidation – as opposed to stations not being ready, difficulties with access agreements and so on – was the point of the passenger delay. I agree that getting every penny of revenue in asap was a matter of life and death for much of the secondary railway system, but consolidating embankments before running a passenger service doesn’t seem to have figured as a critical issue – possibly, a “nice to have” at best. (And even that assumes that the Victorians actually understood the need for consolidation) Pedantic of Purley In other words believing there was a cause and an effect when in fact there was none.

Jonathan Roberts 27 August 2015 at 10:21 @GH In London currently, so don’t have my copies of ‘North of Leeds’ by Peter Baughan or George Dow’s Great Central trilogy to hand, to check the ‘phph’ circumstances with those! Answers later tonight… Graham H 27 August 2015 at 10:52 @JR – Vol2 of Dow makes no comment on specific measures to consolidate embankments by running freight except on p336, where he states a propos the opening of the London extension “There had been heavy rains during the past three months and embankments which had been firm were now giving trouble with slips. He [Parry, the engineer] thought the service should begin with trains stopping at all or most stations”. No such nod to the engineering advice took place, in fact. Passenger services began on 15 March with freight following on 10 and 11 April. No sign of running-in the London extension – the freight receiving offices and depot at Marylebone were not ready until April.

i don’t have North of Leeds [For those of us who were intimately involved in the closure decision, I thought it too depressing…] Jamesthegill Enjoyed the article, with just one minor correction – the link to IanVisits’, er, visit, points back to this very article. Malcolm 27 August 2015 at 14:30 PoP says “believing there was a cause and an effect when in fact there was none” If I could have a pedantic moment, it is really “believing there was a cause and effect when in fact there was no evidence of a cause and effect”. (It would still have been a fallacy even if it further evidence later showed that there was cause and effect.) I’ll go back to my bog now. Graham H 28 August 2015 at 08:03 @Graham H Settle-Carlisle Line: Basically the evidence is that the earlier running of goods trains was because the railway wasn’t yet ready for passenger traffic – indeed some station works weren’t taken in hand until quite late on. Consolidation of the formation was a secondary benefit. Getting the goods trains running was important commercially.

Peter Baughan reports in ‘North of Leeds’ that goods trains started running on 3rd August 1875, “the opening of the line to goods traffic preceded the inspection by the Board of Trade by almost a month” although another inspector had by then checked the Settle Junction. In October the Midland Railway’s engineer, Crossley, was “pleased to say that heavy rains during September had not damaged the works in any way – in fact the combined attention of the rain and the goods trains was consolidating the formation in a very effective way”. Mineral trains from the Craven Lime sidings had already been using the southern end of the line for about two years. In February 1876 the BoT took a week to inspect the line, and reported that there was still a lot to do before the line and station facilities were ready for passengers. It was not until late April that the BoT said that the line might now be used for passenger trains. Those began on May Day 1876. GCR London extension: As you commented above, but also note that coal trains began much earlier, in July 1898 though with legal complexities arising with the Metropolitan Railway.

George Dow writes (p.305 of Vol.2) that “with interest [on the extension] now amounting to £1,000 a day he [Pollitt, the General Manager] wanted to begin running coal trains at the earliest possible opportunity”. Overall, as I noted above, freight and especially coal was the primary earner for Victorian main line railway companies, so there was a commercial and shareholder reason for getting freight running as soon as possible, quite apart from any benefits of track or ground consolidation. The evidence from these two large scale schemes is that the commercial pressures were dominant, and that any consolidation outcomes were a secondary consideration at best. Graham H 28 August 2015 at 08:27 @JR -thanks for that – as I thought, it wasn’t standard practice, as Anonymous 2 believed, to run coal early to consolidate the earthworks, but something you did – if you had the traffic – to bring the cash in asap, with the consolidation as a side benefit.

Incidentally, Parry’s comments (passim) imply that the GC’s coal trains didn’t do a very good consolidation job which further suggests that Fandroid’s plodding horses and navvies’ boots would have been even less effective! Kate Demonstration 28 August 2015 at 09:27 On the related topic of archiving geophysical data – seismic, ground radar, electro-magnetic, bore-hole logs, etc. This is an extremely valuable long-term resource, very expensive to generate, but a major problem is retrieving the data. The problem is not so much deterioration of the media – magnetic tape, discs, paper tape – but in maintaining the readers and associated software. I gather there are racks of archived seismic recordings that can never be used because the readers are no longer working. John Bull 28 August 2015 at 09:31 The problem is not so much deterioration of the media – magnetic tape, discs, paper tape – but in maintaining the readers and associated software. Not just a problem in this field either – so much digital history is at risk or almost gets lost because of this – the BBC’s 1986 Domesday project for example .

Must admit it’s a topic that fascinates me. RayK 29 August 2015 at 10:29 Graham H ‘Parry’s comments (passim) imply that the GC’s coal trains didn’t do a very good consolidation job which further suggests that Fandroid’s plodding horses and navvies’ boots would have been even less effective!’ Given that hooves and boots would have consolidated individual layers it could potentially have been more effective than trains: which would have had most effect on the topmost layers. It would however have been very hit and miss, both because it was not deliberate and because the layers would have varied greatly in thickness. Indeed, some of the layers would have been anything but horizontal. To be sure we would have to conduct a variety of experiments which I suspect would just duplicate work already done. Graham H 29 August 2015 at 11:29 @RayK – I look forward to the practical recreation of this research!

[Not nearly asmuch fun,tho’ as a Cambridge PhD thesis described in the calendar as a study of the movement of smooth water craft in confined spaces when the Reynolds number was less than X* – this turned out to be a study of barges in locks – no doubt conducted pint in hand] * This may be vaguely on topic as I believe the Reynolds number is a measure used in fluid mechanics,but others will tell me better,I’m sure. Greg Tingey 29 August 2015 at 21:05 GH Reynolds Number – is dimensionless, because it is a ratio of forces & is used to detremine if fluid flow is laminar, turbulent, or in-between. NOT to be confused with the really important equation(s) “Navier-Stokes” governing the flow of fluids – including things like steam in locomotive pipery &/or the movement of compressed gases in diesel engines [ See – it’s relevant! ] which are complete bastards to handle, & which have not been solved for all eventualities. One reason why it’s such an important engineering field.

In another life, I used to try to play with some of the practical eventualities of such things: we wanted to see how fast we could lay down simultaneous layers of liquids, without turbulent mixing, & computers could not handle it. The last time I heard, they still couldn’t a lot of the time. See also Turbulent flow & “Karmann Straße” conditions. Greg Tingey 29 August 2015 at 21:10 Update. One of the Clay Prizes in Mathematics ( $1 million ) is up for a complete solution of the “N-S” equations. It’s that important. 30 August 2015 at 01:35 What might be of interest is that when the theory of Critical State Soil Mechanics was being developed at Cambridge in the 1970’s, the stress required for plastic deformation of saturated clay was similar to the stress exerted by a an Irish navvies boot heel. (Also used to ‘puddle’ canal lining.) CSS was important in understanding the behaviour of London Clay – see the construction of the Jubilee tube next to House of Commons, and of course Crossrail tunneling and the increased height of buildings in London.

Foundation settlement is very much controlled by permeability – the rate water can flow through the structure. What I find amazing is that the Liverpool-Manchester line laid over over Chat Moss bog on a floating mattress is still in use. Anomnibus 30 August 2015 at 05:34 Re. track consolidation… During my research into SE London and Kent’s rail networks, I learned that shingle (from Dungeness) was originally used for ballast. At the time — the early-mid 1800s — this was fine, but by the time of the Southern Railway, trains had become both faster and heavier* and the shingle was causing problems. This is believed to have contributed to the fatal Sevenoaks derailment in 1927 . Re. the freight vs. passenger services debate: As is so often the case, the answer is: “It depends.” In the 19th Century, it was common practice for a new line to be promoted by a (not always) independent private company, each backed and led through the necessary Parliamentary Acts by a group of shareholders with their own vested interests and agendas, such as mines, industries, hotels, tourism, and the like.

Hotels and spa towns (which were very popular at the time) would inevitably push for passengers first and foremost. Industrialists, like owners of mines, breweries, ports, etc., would tend to prioritise freight**. If the line was built by a freight-centric company, chances are, it would have prioritised freight, while a passenger-centric company would not. But mistakes happen**, and for more complex routes, the shareholder mix may be such as to make it a toss-up which type of service ‘wins’. * (So, despite the occasional moans about the increased weight of the shiny new trains that have entered service in recent years, this is hardly a new phenomenon.) ** (Captain Cock-up has had a very long and distinguished career that continues to this day, so even if passenger services were the primary objective, it’s quite possible that unexpected issues, such as problems with stations, or cruel and unusual geology discovered while digging tunnels, means freight services were first out of the starting gate.) RayK Kate Demonstration This sounds like the sort of experimentation that I had in mind. Whilst navies boots were deliberately used to puddle clay for canals, is there any evidence that they were as deliberately used to compact railway embankments?

I suspect that, if they were, then that usage might well have been passed on by word of mouth rather than documented. Whilst Chat moss was traditionally referred to as bottomless, it is now know to be up to 9 m deep having been a lake in it’s origins about 10,000 years ago. I’m not convinced that the floating mattress idea is the whole story of the Chat Moss line. The mattress provided a coherent bed binding together as well as supporting the soil and stones which alone were inclined to disperse in the almost liquid bog. I suspect that the ‘floating’ is as apocryphal as the ‘bottomless’. Are there any similar features on lines more directly connected with London? timbeau 30 August 2015 at 19:55 The Little Woodcote area, near the northern edge of the North Downs, should drain freely, since there is chalk below the top soil layer. However, in fields around the Telegraph Track, rainwater will tend to puddle and lie. Apparently the area was used to dump the clay spoil from the Northern Line’s extension to Morden. The tunnelers of the other deep level tubes must have need to dump spoil.

Where did they go? CdBrux 4 September 2015 at 15:00 There is now, unfortunately, a good example of the benefits of knowing as best as possible the geology of the ground you will be tunnelling through to aid project planning. The reboring of the Farnworth tunnel between Bolton & Manchester is proceeding at about half the planned pace as, despite having made a lot of ground sampling before starting, they have hit unforeseen poor conditions – basically a lot of sand falling into the tunnel – and are now injecting some sort of grout ahead of the tunnelling machine to stabilise it. What is not mentioned in that press release is that the tunnel was constructed as a cut and cover tunnel – it seems the cover filled back was any old rubbish they had to hand! ngh 4 September 2015 at 15:26 Re CdBrux, Looking at some of the photos on the NR page it looks like they also back filled with straw!!! Kate Demonstration

Question: Which large marsh,once thought bottomless, lies between Liverpool and Manchester?
Answer: CHAT MOSS